The International Space Station has been orbiting Earth for the past 15 years. It is being used as an international research station, operated jointly by the US-American space agency NASA, the Russian space agency Roscosmos, the European Space Agency (ESA), as well as the space agencies of Canada (CSA) and Japan (JAXA). Since it was commissioned in November 2000, a total of 216 astronauts have flown to the space station to expand it and to work on a variety of research projects. More than 900 experiments from 63 countries have been conducted since 2001. These include research on how plants orient themselves in zero gravity, why humans suffer muscle and bone loss in space and how the cells of the human immune system react to a weightless environment. It is already known that the immune system of the astronauts weakens in space. In fact, the immune system in space is comparable with the lower immune system in old age, explains Alexandra Deschwanden, head of the BIOTESC team of the Lucerne University of Applied Sciences and Arts. Early in January 2015, the team sent two research projects to the ISS on board the SpaceX Dragon capsule. Technical equipment, such as various laboratory devices, is essential for the experiments on board the ISS. Robots that can perform the tasks of astronauts or assist them also play a decisive role

Special robot experiment
One such experimental robot, called “REX-J” (Robot Experiment on JEM), has been in use in Kibo, the Japanese module of the ISS, since 2012 to 2013. He was developed by the JAXA space authority. The objective of the experiment is to develop a new generation of robots (astrobots) capable of moving across the surface of the space station and inside it, to move loads or to perform inspections.
What makes the robot unique is its special locomotion system, which uses tether mechanisms to support the robot. With hooks, the tethers are attached to the existing hand rails that the astronauts use to secure themselves during extravehicular activity on the ISS. The mobile robot is equipped with an extendable arm. At the end of the arm, there is a robot hand that is capable of attaching the tether cables to up to three different anchoring points. This allows the robot to move across a surface like a spider. The robot is operated by the remote control from ground, so that no support from the ISS crew is required.

Powerful drive systems for precision movements
The REX-J is equipped with several drive systems made by maxon motor – and so is the robot extendable arm. The wrist joint has two degrees of freedom: vertical and horizontal. The wrist joint and extendable arm contain brushless EC max motors, planetary gearheads and encoders. There are the control electronics for the motors in the end of the arm. Additional maxon drive systems are also used in the rotary mechanism of the robot and in the cable spool (roll-up mechanism).

All experiments with REX-J have been completed successfully. JAXA will now develop the robot system further, with the aim of using such robots for a range of different tasks on the space station in future. These include monitoring ISS devices and performing visual inspections of the space station, to detect damage to the outer hull. Another long-term goal is to build mobile astrobots that can operate large structures in space.